// C# Eval Expression

// Doc: https://eval-expression.net/options

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// @nuget: Z.Expressions.Eval

​

/*

## MissingTypes

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The MissingType option lets you get or set the missing types to make an expression valid. The list is automatically populated when the option `AutoAddMissingTypes` or `RetryAndThrowMissingTypes` is used. By default, the MissingType value is `null`.

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In this example, we will try to evaluate an expression the first time without the `AutoAddMissingTypes` option, which will fail. Then we will evaluate the expression with the option `AutoAddMissingTypes = true`, which will succeed, and then we will show which missed types we automatically added. Finally, we will try again with the option `RetryAndThrowMissingTypes = true;` and show which types are missing to make the expression work.

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See more: https://eval-expression.net/options

*/

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using System;

using System.Collections.Generic;

using Z.Expressions;

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public class Program

{

    public static void Main()

    {

        // Global Context: EvalManager.DefaultContext.MissingTypes;

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        try

        {

            var context = new EvalContext();

            var fail = (Entity)context.Execute("return new Entity() { EntityID = 13 }");

        }

        catch(Exception ex)

        {

            Console.WriteLine("1 - Exception: " + ex.Message);

        }

        // Using the `AutoAddMissingTypes`

        {

            var context = new EvalContext();

            context.AutoAddMissingTypes = true;

            var entity = (Entity)context.Execute("return new Entity() { EntityID = 13 }");

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            Console.WriteLine("2 - EntityID: " + entity.EntityID);

            foreach(var missingType in context.MissingTypes)

            {

                Console.WriteLine("3 - Missing Types: " + missingType.FullName);

            }

        }

        // Using the `RetryAndThrowMissingTypes`

        {

            var context = new EvalContext();

            context.RetryAndThrowMissingTypes = true;

            try

            {

                var entity = (Entity)context.Execute("return new Entity() { EntityID = 13 }");

            }

            catch(Exception ex)

            {

                Console.WriteLine("4 - Exception: " + ex.Message);

                foreach(var missingType in context.MissingTypes)

                {

                    Console.WriteLine("5 - Missing Types: " + missingType.FullName);

                }

            }           

        }

    }

    public class Entity

    {

        public int EntityID { get; set; }

    }

}

​

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